The invention relates to improvements in methods of and in apparatus for regulating the moisture content of tobacco in cigarettes, cigars, cigarillos or other rod-shaped smokers' products. More particularly, the invention relates to improvements in methods of and in apparatus for uniformizing the moisture content of fillers in rod-shaped smokers' products or of any other fibrous materials which are used in the tobacco processing industry.
The following description of the invention will deal primarily or exclusively with the making of cigarettes. However, it is to be understood that the method and apparatus of the present invention can be used with equal or similar advantage for the making and treatment of other rod-shaped or otherwise configurated smokers' products.
In the making of cigarettes, the distributor or hopper of a cigarette rod making machine turns out a continuous flow of moist tobacco which normally contains a surplus of moisture and which also contains a surplus of tobacco particles. Therefore, it is necessary to equip the cigarette maker with a trimming or equalizing device which removes the surplus so as to convert a portion of the flow into a trimmed stream which is ready for conversion into the filler of a continuous cigarette rod. It is further necessary to reduce the moisture content of the stream so as to ensure that the moisture content of tobacco particles in the filler of the cigarette rod (and hence in the fillers of discrete plain cigarettes) will match or closely approximate the desired optimum value.
German Offenlegungsschrift No. 22 11 520 discloses a method of and an apparatus for uniformizing the moisture content of a filler which is to be confined in a web of cigarette paper or other suitable wrapping material. The initial moisture content of tobacco particles which enter the distributor of the rod making machine exceeds the desired value. The apparatus is intended to be designed in such a way that automatic and/or intentionally induced drying of tobacco particles during travel through the machine should ensure a desired reduction of the moisture content ahead of the draping station. Thus, some drying of tobacco particles is expected to take place in the course of the classifying operation (this involves segregation of fragments of ribs or other heavier particles from shreds of tobacco leaf laminae), and additional drying of tobacco particles is expected to take place during transport toward the stream building zone. The aforementioned German printed application further proposes to enhance the likelihood of a reduction of the moisture content of tobacco particles to a desired value by monitoring the moisture content of tobacco particles ahead of the stream forming station and by heating the entire mass of tobacco particles which are to advance to the stream forming zone by one or more currents of heated air. The temperature of drying air is regulated in dependency on the results of the moisture monitoring operation.
A drawback of the just discussed method and apparatus is that the reduction of moisture content of tobacco particles is premature, i.e., the particles undergo a pronounced drying action well ahead of the station where the filler of tobacco particles is draped into a web of cigarette paper. This is undesirable because tobacco particles having a relatively high moisture content are less likely to be comminuted than relatively dry tobacco particles, i.e., the percentage of short tobacco and other undesirable fragments of tobacco leaves which are admitted into the distributor is lower if the moisture content of tobacco particles is reduced at a late or very late stage of conversion into the filler of a cigarette rod. Comminution of tobacco particles can take place at a plurality of locations in the interior of a modern distributor wherein the particles are acted upon by carded conveyors, picker rollers and other devices which spear, propel and/or otherwise manipulate the particles on their way toward the tobacco stream building zone. The filling power of a filler which consists primarily of long or reasonably long shreds of tobacco leaf laminae is much more satisfactory than that of a filler which contains a relatively high percentage of short tobacco.
Another drawback of presently known proposals to uniformize the moisture content of tobacco particles in the filler of a cigarette rod or in the fillers of discrete cigarettes is that such known undertakings fail if the moisture content of tobacco which enters the distributor fluctuates within a rather wide range. Mere drying with heated air is not always sufficient to reduce the moisture content to a desired value, and such drying may be too pronounced if the initial moisture content of tobacco particles is rather low.